GLOBAL WARMING'S IMPACT ON WILDLIFE

Dear EarthTalk: Ive seen those
images of polar bears stranded on small islands of ice and
heard that some are now dying by drowning.
How are other wildlife populations affected by global warming?

Jessie Walters, via e-mail

Most researchers agree that even small changes in temperature are
enough to send hundreds if not thousands of already struggling species
into extinction unless we can stem the tide of global warming. And time
may be of the essence: A 2003 study published in the journal
Nature concluded that 80 percent of some 1,500 wildlife species
sampled are already showing signs of stress from climate change.

The key impact of global warming on wildlife is habitat displacement,
whereby ecosystems that animals have spent millions of years adapting to
shift quickly. Ice giving way to water in polar bear habitat is just one
example of this. Another, according to The Washington Post, is
the possibility that warmer spring temperatures could dry up critical
breeding habitat for waterfowl in the prairie pothole region, a stretch of
land between northern Iowa and central Alberta.

Affected wildlife populations can sometimes move into new spaces and
continue to thrive. But concurrent human population growth means that many
land areas that might be suitable for such "refugee wildlife" are already
taken and cluttered with residential and industrial development. A recent
report by the Pew Center for Global Climate Change suggests creating
"transitional habitats" or "corridors" that help migrating species by
linking natural areas that are otherwise separated by human
settlement.

Some of the wildlife species hardest hit so far
by global warming include caribouPhoto: Getty Images

Beyond habitat displacement, many scientists agree that global warming
is causing a shift in the timing of various natural cyclical events in the
lives of animals. Many birds have altered the timing of long-held
migratory and reproductive routines to better sync up with a warming
climate. And some hibernating animals are ending their slumbers earlier
each year, perhaps due to warmer spring temperatures. To make matters
worse, recent research contradicts the long-held hypothesis that different
species coexisting in a particular ecosystem respond to global warming as
a single entity. Instead, different species sharing like habitat are
responding in dissimilar ways, tearing apart ecological communities
millennia in the making.

And as wildlife species go their separate ways, humans can also feel
the impact. A World Wildlife Fund study found that a northern exodus from
the United States to Canada by some types of warblers led to a spread of
mountain pine beetles that destroy economically productive balsam fir
trees. Similarly, a northward migration of caterpillars in the Netherlands
has eroded some forests there.

According to Defenders of Wildlife, some of the wildlife species
hardest hit so far by global warming include caribou (reindeer), arctic
foxes, toads, polar bears, penguins, gray wolves, tree swallows, painted
turtles and salmon. The group fears that unless we take decisive steps to
reverse global warming, more and more species will join the list of
wildlife populations pushed to the brink of extinction by a changing
climate.